Giant superconducting ring takes a road trip

It looks like an alien spaceship about to take off on an intergalactic adventure. In reality this gargantuan object is a ring of superconducting magnets made by human hands, but its current journey is as bizarre as any a spacecraft might make.

The 15-metre-diameter ring was originally used at Brookhaven National Laboratory in New York to measure the magnetism of the muon, a subatomic particle that is essentially a heavier version of the electron. Now researchers at Fermilab in Batavia, Illinois, want to use it for a new experiment called Muon g-2. The only problem is moving it to its new home, about a third of the way across the US.

Scientists from three Department of Energy national laboratories, Fermilab, Brookhaven and Argonne, along with scientists from seven foreign countries and more than a dozen U.S. universities are collaborating on a new physics experiment that will probe fundamental properties of matter and space. Muon g-2 (pronounced gee minus two) is an Intensity Frontier experiment that will allow researchers to peer into the subatomic world to search for undiscovered particles that may be hiding in the vacuum.

Soon to be built at Fermilab’s new Muon Campus, the experiment will use the Fermilab accelerator complex to produce an intense beam of muons traveling at nearly the speed of light. Scientists will use the beam to precisely determine the value of a property known as the g-2 of the muon.

The muon, like its lighter sibling the electron, acts like a spinning magnet. The parameter known as "g" indicates how strong the magnet is and the rate of its gyration. The value of g is slightly larger than 2, hence the name of the experiment. This difference from 2 is caused by the presence of virtual particles that appear from the vacuum and then quickly disappear into it again.

In measuring g-2 with high precision and comparing its value to the theoretical prediction, physicists will discover whether the experiment agrees with theory. Any deviation would point to as yet undiscovered subatomic particles that exist in nature.

An experiment that concluded in 2001 at Brookhaven National Laboratory found a tantalizing greater-than-3-sigma (standard deviation) discrepancy between the theoretical calculation and the measurement of the muon g-2. The level necessary for claiming a discovery is 5 sigma. Fermilab will pick up where Brookhaven left off, making an even more precise measurement.

With a four-fold increase in the measurement’s precision, Muon g-2 will be more sensitive to virtual or hidden particles and forces than any previous experiment of its kind. [...] Source